GTO
Gate Turn-Off Thyristor
Libraries:
Simscape /
Electrical /
Semiconductors & Converters
Description
The GTO block models a gate turn-off thyristor (GTO). The I-V characteristic of a GTO is such that if the gate-cathode voltage exceeds the specified gate trigger voltage, the GTO turns on. If the gate-cathode voltage falls below the specified gate turn-off voltage value, or if the load current falls below the specified holding-current value, the device turns off .
To define the I-V characteristic of the GTO, set the On-state behaviour and
switching losses parameter to either Specify constant
values
or Tabulate with temperature and
current
. The Tabulate with temperature and
current
option is available only if you expose the thermal port of the
block.
In the on state, the anode-cathode path behaves like a linear diode with forward-voltage drop, Vf, and on-resistance, Ron. However, if you expose the thermal port of the block and parameterize the device using tabulated I-V data, the tabulated resistance is a function of the temperature and current.
In the off state, the anode-cathode path behaves like a linear resistor with a low off-state conductance value, Goff.
The defining Simscape™ equations for the block are:
if ((v > Vf)&&((G>Vgt)||(i>Ih)))&&(G>Vgt_off) i == (v - Vf*(1-Ron*Goff))/Ron; else i == v*Goff; end
where:
v is the anode-cathode voltage.
Vf is the forward voltage.
G is the gate voltage.
Vgt is the gate trigger voltage.
i is the anode-cathode current.
Ih is the holding current.
Vgt_off is the gate turn-off voltage.
Ron is the on-state resistance.
Goff is the off-state conductance.
Using the Integral Diode parameters, you can include an integral cathode-anode diode. A GTO that includes an integral cathode-anode diode is known as an asymmetrical GTO (A-GTO) or reverse-conducting GTO (RCGTO). An integral diode protects the semiconductor device by providing a conduction path for reverse current. An inductive load can produce a high reverse-voltage spike when the semiconductor device suddenly switches off the voltage supply to the load.
The table shows you how to set the Integral protection diode parameter based on your goals.
Goal | Value to Select | Block Behavior |
---|---|---|
Prioritize simulation speed. | Diode with no dynamics | The block includes an integral copy of the Diode block. To parameterize the internal Diode block, use the Protection parameters. |
Precisely specify reverse-mode charge dynamics. | Diode with charge dynamics | The block includes an integral copy of the dynamic model of the Diode block. To parameterize the internal Diode block, use the Protection parameters. |
Model Gate Port and Thermal Effects
You can choose between physical or electrical ports to control the gate terminal and expose
the thermal port to model the heat that switching events and conduction losses
generate. To choose the gate control port, set the Gate control
port parameter to PS
or
Electrical
. To expose the thermal port, set the
Modeling option parameter to either No
thermal port
or Show thermal
port
.
For more information about using thermal ports, see Simulating Thermal Effects in Semiconductors.
Thermal Losses
The figure shows an idealized representation of the output voltage, Vout, and the output current, Iout, of the semiconductor device. The interval shown includes the entire nth switching cycle, during which the block turns off and then on.
Switching losses are one of the main sources of thermal loss in semiconductors. During each on-off switching transition, the GTO parasitics store and then dissipate energy.
Switching losses depend on the off-state voltage and the on-state current. When the switching device is turned on, the power losses depend on the initial off-state voltage across the device and the final on-state current once the device is fully in its on state. Similarly, when the switching device is force commutated off, the power losses depend on the initial on-state current through the device and the final off-state voltage once the device is fully in its off state. The switch on and force commutated switch off losses are either fixed or dependent on junction temperature and drain-source current, depending on how you specify the On-state behavior and switching losses parameter. In both cases, the losses are scaled by the off-state voltage prior to the latest device turn-on event.
When the current falls below the holding current and the device is naturally commutated off, the losses are set by the Natural commutation rectification loss parameter. Because it’s not possible to know when to measure the starting current or final voltage for the rectification loss, it is not possible to scale it by the off-state voltage or on-state current.
In this block, switching losses are applied by stepping up the junction temperature with a value equal to the switching loss divided by the total thermal mass at the junction.
Note
As the final current after a switching event is not known during the simulation, if you use the GTO block as a fully-controlled device, the block records the on-state current at the point that the device is commanded off. If you use the GTO block as a partially-controlled device, the block records the on-state current once the current is greater than the holding current for a time longer than the value of the Wait time before switch-on current measurement parameter. Similarly, the block records the off-state voltage at the point that the device is commanded on. For this reason, the simlog does not report the switching losses to the thermal network until one switching cycle later
For all ideal switching devices, the switching losses are reported in the
simlog as lastTurnOffLoss
and
lastTurnOnLoss
and recorded as a pulse with amplitude
equal to the energy loss. If you use a script to sum the total losses over a
defined simulation period, you must sum the pulse values at each pulse rising
edge. Alternatively, you can use the ee_getPowerLossSummary
and
ee_getPowerLossTimeSeries
functions
to extract conduction and switching losses from logged data.
Note that the power_dissipated
variable in the simlog does
not include switching losses as they are modeled as instantaneous events. The
power_dissipated
variable therefore just reports
instantaneous on-state losses.
Reverse recovery loss is one of the main sources of thermal loss in diodes. The diode dissipates energy every time it turns off, from its conducting state to the open-circuit state.
In this block, reverse recovery losses are applied by stepping up the junction temperature with a value equal to the reverse recovery loss divided by the total thermal mass at the junction.
If you set the Reverse recovery loss model parameter to Tabulated loss
, the value of the Reverse recovery loss table, Erec(Tj, If) parameter specifies the dissipated energy in function of the junction temperature and the forward current just before the switching event. The off-state voltage linearly scales the losses prior to the latest device turn-off event. The table uses delayed values for current and voltage. To ensure the value used in the lookup table is close enough to the instantaneous value, set the Delay for voltage and current tabulation parameter to a value that is lower than the fastest switching period.
If you set the Reverse recovery loss model parameter to
Fixed loss
, the value of the Reverse recovery
loss parameter specifies the dissipated energy in each turn-off event,
regardless of the state of the diode before or after the switching event.
Note
The lastReverseRecoveryLoss
variable in the simlog includes the
reverse recovery losses as a pulse with amplitude equal to the energy loss. If you use a
script to sum the total losses over a defined simulation period, you must sum the pulse
values at each pulse rising edge. Alternatively, you can use the ee_getPowerLossSummary
and ee_getPowerLossTimeSeries
functions to extract conduction and switching
losses from logged data.
Note that the power_dissipated
variable in the simlog does not
include switching losses as they are modeled as instantaneous events. The
power_dissipated
variable reports instantaneous on-state
losses.
Variables
To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.
Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see System Scaling by Nominal Values.
Examples
Ports
The figure shows the block port names.